The appeal of Usopp and Perona as a ship often starts with those shared insecurities underneath the bluster, and I think fanfics that zero in on that are the ones that nail their growth the best. You see Usopp, who has to build this whole persona just to function in a crew of monsters, and Perona, whose whole ghost-princess act is a shield against a world that’s frankly terrifying without Moria’s protection. They’re both performing confidence from opposite ends—he’s inflating himself, she’s deflating everyone else—and stories that unpack that similarity are gold. Their development usually isn’t a linear hero’s journey; it’s messier, with setbacks that feel true to both characters. Like, a fic might have Usopp trying to teach her basic survival skills on a whim, only for her to get frustrated and summon a bunch of negative hollows, which of course feeds into his own panic. But instead of it being a disaster, they have to talk it out, and that conversation becomes the growth moment. He admits his fear of looking useless, she admits her fear of being alone and incapable. It’s vulnerability that drives the change, not just plot events.
I’ve read a few where the setting is post-timeskip, with Perona sort of adrift after everything at Thriller Bark and Marineford, and she ends up tracking down the Straw Hats—or just Usopp—out of a weird, grudging curiosity. Those are great for slow-burn development because you get to see Usopp’s increased competence from the timeskip rubbing off on her. He’s not just a liar anymore; he’s a craftsman, a strategist, someone who builds things. And Perona, stripped of her kingdom, starts to appreciate that kind of tangible skill. Her growth becomes about finding a purpose that isn’t tied to being a spoiled princess or a subordinate, but as someone who can contribute in her own way, maybe using her ghost powers for reconnaissance or morale in ways Usopp would brainstorm. Their dynamic shifts from two scared kids pretending to be tough to two people who quietly make each other braver, and I find that way more satisfying than any big, flashy romantic confession. The growth is in the small, practical things—like Perona learning to mend her own clothes without using a ghost, or Usopp admitting he’s scared before a fight without it breaking him.